I thought they were confirming the mutant angle and the powers she was born with is what kept the Stark missile dormant and kept her and her brother safe(whats the real chance of a start missile not working w/ the rep of starks stuff)They avoided the answering this because it would force them to confirm/deconfirm if they are mutants or not.
then her coming in contact w/ the mind stone took her powers to another level
unless we buying it was a dud missile